Due to recent advances in genetic and cell engineering technologies, proteins known to exhibit various pharmacological actions in vivo are capable of being produced in large amounts for pharmaceutical applications. Such pharmaceutical proteins include erythropoietin (EPO), novel erythropoiesis stimulating protein (NESP), granulocyte colony-stimulating factor (G-CSF), interferons (alpha, beta, gamma, consensus), tumor necrosis factor binding protein (TNFbp), interleukin-1 receptor antagonist (IL-1ra), brain-derived neurotrophic factor (BDNF), kerantinocyte growth factor (KGF), stem cell factor (SCF), megakaryocyte growth differentiation factor (MGDF), osteoprotegerin (OPG), glial cell line derived neurotrophic factor (GDNF), somatotrophins and obesity protein (OB protein). OB protein may also be referred to herein as leptin.
Many illnesses or conditions treated with pharmaceutical proteins require sustained protein levels to achieve the most effective therapeutic result. However, as with most protein pharmaceuticals, the generally short biological half-life requires frequent administration. These repeated injections are given at various intervals which result in fluctuating medication levels at a significant physical and monetary burden on the patients. Since many conditions respond better to controlled levels of a pharmaceutical, a need exists for controlled release of a medicament to provide longer periods of consistent release. Such sustained-release medicaments would provide a means of controlling blood levels of the active ingredient, thus providing the patient with enhanced prophylactic, therapeutic or diagnostic effects, as well as greater safety, patient convenience and patient compliance. Also such sustained release compositions can lead to dose sparing and thus lower cost of protein production. Unfortunately, the instability of most proteins (e.g. denaturation and loss of bioactivity upon exposure to heat, organic solvents, etc.) has greatly limited the development and evaluation of sustained-release formulations.
Attempts to develop sustained-release formulations have included the use of a variety of biodegradable and non-biodegradable polymer (e.g. poly(lactide-co-glycolide)) microparticles containing the active ingredient (see e.g., Wise et al., Contraception, 8:227–234 (1973); and Hutchinson et al., Biochem. Soc. Trans., 13:520–523 (1985)), and a variety of techniques are known by which active agents, e.g. proteins, can be incorporated into polymeric microspheres (see e.g., U.S. Pat. No. 4,675,189 and references cited therein). Unfortunately, some of the sustained release devices utilizing microparticles still suffer from such things as: low entrapment efficiency; active agent aggregation formation; high initial bursts of active agent with minimal release thereafter; and incomplete release of active agent.
Other drug-loaded polymeric devices have also been investigated for long term, therapeutic treatment of various diseases, again with much attention being directed to polymers derived from alpha hydroxycarboxylic acids, especially lactic acid in both its racemic and optically active form, and glycolic acid, and copolymers thereof. These polymers are commercially available and have been utilized in FDA-approved systems, e.g., the Lupron Depot™, which consists of injectable microparticles which release leuprolide acetate for about 30 days for the treatment of prostate cancer.
Various problems identified with the use of such polymers include: inability of certain macromolecules to diffuse out through the matrix; deterioration and decomposition of the drug (e.g., denaturation caused by the use of organic solvents); irritation to the organism (e.g. side effects due to use of organic solvents); low biodegradability (such as that which occurs with polycondensation of a polymer with a multifunctional alcohol or multifunctional carboxylic acid, i.e., ointments); and slow rates of degradation.
A variety of oil based formulations have been described. Welch in U.S. Pat. No. 2,491,537 discloses the use of oil suspensions (gelled vegetable oil) to provide 24 hour release of penicillin. Buckwalter in U.S. Pat. No. 2,507,193 discloses release in rabbits for up to eleven days using procaine penicillin suspended in peanut oil gelled with 5% aluminum monostearate (AIMS). Anschel in U.S. Pat. No. 2,964,448 discloses suspensions of relaxin in a vegetable oil gelled with AIMS. Anschel reports 5–7 days of relaxation and discloses longer effect (up to 23 days) by heat treating the suspension containing AIMS. Yamahira et al. in U.S. Pat. No. 4,855,134 disclose sustained-release preparations of indomethacin or interferon in admixture with a pharmaceutically acceptable biodegradable carrier, e.g., gelatin. Mitchell in U.S. Pat. No. 5,411,951 discloses compositions wherein metal-associated somatotropin is present in a biocompatible oil and it is demonstrated that the compositions can be parenterally administered for prolonged release of somatotropin in animals. Ferguson et al. in U.S. Pat. No. 4,977,140 disclose sustained release formulations comprising bovine somatotropin, a wax, and an oil. Reichert et al. in WO 96/18417 disclose pharmaceutical compositions comprising mixtures of crystalline G-CSF and vegetable oils.
There have also been a number of reports discussing efforts to develop drug delivery systems utilizing protein that are subject to aggregation. For example, Grodsky et al., U.S. Pat. No. 4,371,523, describe the use of anti-aggregation agents, e.g., glutamic acid and/or aspartic acid, to develop insulin formulations. Blackshear et al., U.S. Pat. No. 4,439,181, describe mixing glycerol or another polyol with an aqueous protein hormone solution prior to the introduction of the solution into the drug delivery system. Wigness et al., PCT Publication WO 85/02118 describe the use of glycerol to prevent precipitation of proteins within drug delivery systems; and Azain et al., EP Publication 0 374 120 A2 describe stable somatotropin compositions which utilize, inter alia, a stabilizing polyol.
Despite the advances made in the processes described above, there is still a need to develop pharmaceutical formulations which achieve a more versatile and effective means of sustained-release for clinical applications. Numerous recombinant or natural proteins could benefit from constant long term release and thereby provide more effective clinical results.
Human recombinant G-CSF selectively stimulates neutrophils, a type of white blood cell used for fighting infection. Currently, FILGRASTIM®, a recombinant G-CSF, is available for therapeutic use. The structure of G-CSF under various conditions has been extensively studied; Lu et al., J. Biol. Chem. Vol. 267, 8770–8777 (1992).
G-CSF is labile and highly susceptible to environmental factors such as temperature, humidity, oxygen and ultraviolet rays. And, because of its hydrophobic characteristics, G-CSF is difficult to formulate due to formation of dimer and higher order aggregates (macro range) during long-term storage. G-CSF has been shown to be very prone to aggregation, especially at neutral pH, elevated salt and temperatures (i.e. physiological serum conditions). This instability makes the sustained release (of a period of one week or greater) by conventional delivery systems very problematic, and in fact, such systems generally provide only a few days of release at best.
It is an object of the present invention to produce a G-CSF-containing preparation which would provide for the sustained release of G-CSF. Production of such preparations is achieved using glycerol/oil suspensions containing G-CSF, and, importantly, pharmaceutical compositions using these G-CSF/glycerol/oil suspensions are capable of providing increased bioavailability, protein protection, decreased degradation and slow release with increased protein stability and potency. Importantly, pharmaceutical compositions of the present invention provide a simple, rapid and inexpensive means of controlled recombinant protein release for effective prophylactic, therapeutic or diagnostic results.